Add base 'timestamp' schema to datasets model

- adds a new schemas lib
- loads in timestamp schema from a file
- path is hardcoded
- all data-set tests require a schema
![](http://37.media.tumblr.com/e6f577bf0ae642bbde4b4b68a0ddfd09/tumblr_n3ofa6vU5O1sl0ij8o1_500.jpg)
I found `json_f` a bit of a confusing name, took me a few seconds to figure out what it meant. Maybe, `schema` would be more appropriate?